Research On Operation Control Of Single-phase Microgrid System

A microgrid system can integrate the advantages of distributed generation and coordinate the contradiction between distributed generation system and power grid.In the future,it will be an important part of smart grid.However,many key technical problems need to be settled.In this paper,we tried to put forward a more effective operation control strategy,which is of great significance for the development of the microgrid.The major work is presented as follows:Aiming at the photovoltaic power generation in the microgrid system,we emphatically analyzed the control strategy of the double-stage photovoltaic power generation system.On the basis of analyzing the control mode of microgrid and the control strategy of single-phase inverter,a two-layer control strategy is proposed.The module of top-level control is constructed by a central controller and the communication system.The underlying control section is composed of each distributed power controller.A model of master and slave control,which selecting one controller as the master controller and selecting the rest controllers as the slave controllers,is adopted in the underlying control section.In this way,the parallel operation of the inverters in the islanded microgrid can be realized.In addition,the grid-connected control strategy based on two-layer control model can realize the synchronization of the amplitude,frequency and phase of the microgrid voltage and the external power grid voltage,so as to realize the smooth switching of the operating mode of the microgrid.The power balance of the microgrid is guaranteed by the control of the upper communication system and the bottom distributed power supply.The simulation experimental platform of the microgrid is set up.Based on this platform,the switch-in and switch-out of the slave inverters and the load switching in microgrid and the transition of microgrid operation mode are performed.The simulation results showed that the power balance of the microgrid,the smooth transition of the operation mode and the suppression of the load inrush current can be realized based on the proposed control strategy.Finally,the experimental platform was set up to verify the control strategy.We debugged the platform respectively from hardware aspect and software aspect.Then the test of the zero-crossing detection circuit,the inverter on-line debugging,the microgrid operation mode switching test and the load switching test are carried out.The experimental results verify the effectiveness of the control strategy proposed in this paper.